Owning up to their promise of releasing Mac games every Wednesday, Valve has delivered the latest set of Steam for Mac games. The games that are available this week are: Caster, Madballs in Babo Invasion, Killing Floor, Chains, Hearts of Iron III and Altitude.

Along with the release of these titles, Killing Floor is now 33% off for a limited time.

“We were thrilled when we learned that Steam was coming to the Mac platform and started working on a native Mac version of Killing Floor immediately,” said John Gibson, President of Tripwire Interactive, creators of Killing Floor. “Steam’s advanced multiplayer support on both the PC and Mac has enabled us to bring Killing Floor to a whole new audience on the Mac and introduce them to the existing PC player community.”

Altitude will have a free weekend promotion and offered for 50% as well. Madballs has a similar promotion in that you can buy it for just $4.99.